A pneumatic system of the general type under consideration, e.g., disclosed in EP 1 165 333 B2, is used in vehicles of all types. A pneumatic system of this type is used for the suspension and potentially also for level control in a vehicle, so that the distance between the axle of the vehicle and body of the vehicle can be adjusted. An air suspension installation of such type comprises a plurality of bellows, each acting as a pressure chamber for a pneumatic spring, which raises the body of the vehicle with increasing filling and can lower it with decreasing pressurization. With increasing distance between the axle of the vehicle and the body of the vehicle or ground clearance, the spring travels can be longer and more uneven surfaces can also be overcome without this leading to contact with the body of the vehicle. Such pneumatic systems are used in off-road vehicles and sport utility vehicles (SUV). Especially with SUVs with very powerful engines, it is desirable that the vehicle is provided with relatively little ground clearance on the one hand for high speeds on the road and on the other hand with a relatively large ground clearance for off-road. It is further desirable to carry out a change of the ground clearance as rapidly as possible, which increases the requirement for speed, flexibility and reliability of a pneumatic system having an air suspension installation.
A compressed air supply system typically supplies the air suspension system in a pneumatic system with compressed air from a compressed air supply, for example in the region of a pressure level of 5 to 20 bar. The compressed air is supplied by an air compressor of a pressure source. For supplying the air suspension installation, the pressure source is connected to a connection of a pneumatic line of the air suspension installation, which can also be pneumatically connected to a vent. The compressed air supply installation and the air suspension installation can be vented by blowing off air via a venting valve apparatus. A pneumatic supply line of the compressed air supply installation usually comprises an air dryer in order to ensure long-term operation of the compressed air supply installation or to prevent the collection of moisture in the pneumatic system.
A control valve in the form of a solenoid valve—also referred to as a switching valve—is usually connected upstream of each air bellows of the air suspension installation. A control valve is connected to the pneumatic line of the air suspension installation such that the air bellows can be filled or emptied—depending on a switching state of the control valve. In other words, air masses can be adjusted in an air bellows in order to thereby regulate the suspension characteristics or the level for a vehicle.
It is desirable to provide an improved air suspension installation not only with respect to the increasing requirement for speed, flexibility and reliability, but in addition—without having to make restrictions of a functional nature—as simply as possible.